Chapter 6. MPC8240 Memory Interface
6-29
SDRAM Interface Operation
6.2.11 SDRAM Registered DIMM Mode
The MPC8240 can be configured to support registered SDRAM DIMMs. To reduce
loading, registered DIMMs latch the SDRAM control signals internally before using them
to access the array. Enabling the MPC8240’s registered DIMM mode (MCCR4 bit 15,
REGDIMM = 1) compensates for this delay on the DIMMs control bus by delaying the
MPC8240’s data and parity buses for SDRAM writes by one additional clock cycle.
Enabling registered DIMM mode has no affect on the bus timing for SDRAM reads or
ROM/Flash transfers. However, the programmed read latency (RDLAT) time for SDRAM
reads must be incremented by one to compensate for the latch delay on the control signals
of the registered DIMM. Figure 6-15 shows the registered SDRAM DIMM single-beat
write timing.
Table 6-13. The MPC8240 SDRAM ECC Syndrome Encoding (Data Bits 32:63)
Syndrome
Bit
Data Bit
3
2
3
3
3
4
3
5
3
6
3
7
3
8
3
9
4
0
4
1
4
2
4
3
4
4
4
5
4
6
4
7
4
8
4
9
5
0
5
1
5
2
5
3
5
4
5
5
5
6
5
7
5
8
5
9
6
0
6
1
6
2
6
3
0
x
x
x
x
x
x
x
x
1
x
x
x
x x
x
x
x
2
x x x x x x x x x x x x x x x x
x
x
x
x
3
x
x
x
x
x
x
x
x x x x
4
x x x
x x x
x x x
x x x
x x x x
5
x x x x
x x x x x x x x x x x x
6
x x x x x x x x x x x x
x x x x x x x x
7
x x
x x
x x x x
x x x x x x x x
x x x
Summary of Contents for MPC8240
Page 1: ...MPC8240UM D Rev 1 1 2001 MPC8240 Integrated Processor User s Manual ...
Page 38: ...xviii MPC8240 Integrated Processor User s Manual TABLES Table Number Title Page Number ...
Page 48: ...xlviii MPC8240 Integrated Processor User s Manual Acronyms and Abbreviations ...
Page 312: ...6 94 MPC8240 Integrated Processor User s Manual ROM Flash Interface Operation ...
Page 348: ...7 36 MPC8240 Integrated Processor User s Manual PCI Host and Agent Modes ...
Page 372: ...8 24 MPC8240 Integrated Processor User s Manual DMA Register Descriptions ...
Page 394: ...9 22 MPC8240 Integrated Processor User s Manual I2O Interface ...
Page 412: ...10 18 MPC8240 Integrated Processor User s Manual Programming Guidelines ...
Page 454: ...12 14 MPC8240 Integrated Processor User s Manual Internal Arbitration ...
Page 466: ...13 12 MPC8240 Integrated Processor User s Manual Exception Latencies ...
Page 516: ...16 14 Watchpoint Trigger Applications ...
Page 538: ...B 16 MPC8240 Integrated Processor User s Manual Setting the Endian Mode of Operation ...
Page 546: ...C 8 MPC8240 Integrated Processor User s Manual ...
Page 640: ...INDEX Index 16 MPC8240 Integrated Processor User s Manual ...